The term “toxicodependency”, whether physical or psychological, means the continued and totally implicit use of a drug. Such a use involves the risk of physical damage and the need to stop or limit the consumption of the substance, whether or not the drug taker is in agreement.
The term “psychological dependency” means an irresistible impulse (compulsion) to continue self-administering the drug in order to find pleasure. For certain drugs, the psychological dependency is the most important factor in their compulsive use.
The term “physical dependency” means a state of habituation to the drug accompanied by tolerance and that is manifested by abstinence syndromes.
Tolerance is the need to increase the dose of the drug in order to obtain the same effects as were initially obtained with lower doses; the abstinence syndrome is characterized by painful physical sensations that are manifested when the taking of the drug is stopped.
The substances commonly used by drug takers all induce psychological dependency, while others (the majority) also induce physical dependency.
The following groups may be distinguished: CNS sedatives such as opiates, benzodiazepines, barbiturates and alcohol, which also all induce physical dependency and tolerance; CNS stimulants, for instance amphetamine and cocaine which induce physical dependency to a minor extent, if at all; hallucinogens such as LSD, mescalin, cannabis (marijuana) and fencyclidine.
On the basis of published preclinical data, the compound neboglamine (CR 2249) has been shown to have significant modulatory properties on the glycine site (strychnine-insensitive) coupled to the NMDA receptor complex [Lanza et al., Neuropharmacology 36, 1057-64 (1997)], and also advantageous properties of promoting memory and learning in various animal models [Garofalo et al. J. Pharm. Pharmacol. 48, 1290-97 (1996)]. The facilitatory activity exerted by neboglamine on the NMDA receptor complex should be of therapeutic use in conditions of glutamatergic hypofunctionality.
It has been suggested that the NMDA receptor complex may be involved in a variety of functional responses to cocaine, for instance locomotor activity, dependency (continued reinforcement of self-administration), tolerance and toxicity (Rockhold R. W., Progress in Drug Research 50: 155-92, 1998).
It has also recently been demonstrated that glycine is capable of inhibiting the locomotor hyperactivity, tolerance and dependency induced by morphine in mice (K. W. Shin et al., Arch. Pharm. Res. 26: 1074-1078, 2003).